Even where deliberate measures are taken to obtain valid evidence on any political or social question raised, by summoning witnesses of all classes and interests, there is difficulty in getting at the truth; because the circumstances of the inquiry tend of themselves to bring into sight some kinds of evidence, and to keep out of sight other kinds. In illustration may be quoted the following statement of Lord Lincoln on making his motion concerning the enclosures of commons:
"This I know, that in nineteen cases out of twenty, committees sitting in this House on private bills neglected the rights of the poor. I do not say that they wilfully neglected those right—far from it; but this I affirm, that they were neglected in consequence of the committees being permitted to remain in ignorance of the rights of the poor man, because by reason of his very poverty he is unable to come up to London to fee counsel, to procure witnesses, and to urge his claims before a committee of this House."—(Hansard, May 1, 1845.[1])
Many influences of a different order, but similarly tending to exclude particular classes of facts pertinent to an inquiry, come into play. Given a question at issue, and it will very probably happen that witnesses on the one side may, by evidence of a certain nature, endanger a system on which they depend for the whole or for part of their livelihood; and by evidence of an opposite nature may preserve it. By one kind of testimony they may offend their superiors and risk their promotion: doing the reverse by another kind. Moreover, witnesses not thus directly interested are liable to be indirectly swayed by the thought that to name certain facts they know will bring on them the ill-will of important persons in their locality—a serious consideration in a provincial town. And while such influences strongly tend to bring out evidence, say in support of some established organization, there may very possibly, and, indeed, very probably, be no organized adverse interest with abundant resources which busies itself to bring out a contrary class of facts—no occupation in danger, no promotion to be had, no applause to be gained, no odium to be escaped. Contrariwise, there may be positive sacrifices, serious in amount, to be made before such contrary class of facts can be brought to light. And thus it may happen that, perfectly open and fair as the inquiry seems, the circumstances will insure a one-sided representation.
A familiar optical illusion well illustrates the nature of these illusions which often deceive sociological inquirers: When standing by a lake-side in the moonlight, you see, stretching over the rippled surface toward the moon, a bar of light which, as shown by its nearer part, consists of flashes from the sides of separate wavelets. You walk, and the bar of light seems to go with you. There are, even among cultivated people, many who suppose that this bar of light has an objective
